Photosensor-equipped display devices have been proposed that include light detecting elements, such as photodiodes, in the pixels so as to be capable of sensing the brightness of ambient light or capturing an image of an object located close to the display. Typically, such photosensor-equipped display devices may be used as two-way communication display devices or devices with touch panel capabilities.
Such a photosensor-equipped display device is disclosed in JP 2005-275644 A, where a backlight including a combination of two different sets of light sources, each set capable of emitting visible or non-visible light, turns these sets of light sources on at different times to make it possible to detect the location of an object independently from image display.
As discussed above, in a display device with a backlight including a combination of visible and non-visible light sources, the non-visible light sources are driven in a synchronized manner with the sensing of light by the photosensors. A problem with this arrangement is that turning on the non-visible light sources may cause a momentary voltage drop at the backlight.